Q: Do you find more fulfillment in teaching or researching?
A: They are complementary. You only really learn something when you can teach it to someone else. If you have to do something like abstract geometry, you have to be able to do basic geometry really quickly. After you’ve taught calculus a few times you can look at differential equations and say “oh, it should look like this”, which would have taken like half an hour as a student but now takes a few minutes. You need that speed in order to tackle the harder problems, so it is complementary.
Full interview is here.